Necticut



(No Model.) 2 SheetsSheet 1.

E. R. KNOWLES & L. T. ROBINSON. ELECTRICAL MEASURING INSTRUMENT.

No. 516,823. Patented Mai. 20, 1894.

:illillllllllllllll (No Model.) -2 Sheets-Sheet 2.

E. KNOWLES & L. T. ROBINSON. ELECTRIC-AL MEASURING INSTRUMENT.

WI fflassgs- QM 6. ezzwz.

NITE STATES PATENT FFICE.

NECTICUT, ASSIGNORS TO THE SCHUYLER ELECTRIC COMPANY, OF

CONNECTICUT.

ELECTRICAL MEASURING-INSTRUMENT.

SPECIFICATION forming part of Letters Patent No. 516,823, dated March20, 1894.

Application filed February 25, 1893. Serial No. 463,753- (No model.)

To It whom it may concern.-

Be it known that we, EDWARD R. KNOWLES and LEWIS T. ROBINSON, citizensof the United States, residing at Middletown, in the county of Middlesexand State of Connecticut, have invented certain new and usefulImprovements in Electrical Measuring-Instruments; and we do herebydeclare the following to be a full, clear, and exact description of theinvention, such as will enable others skilled in the art to which itappertains to make and use the same, reference being had to theaccompanying drawings, and to the letters and figures of referencemarked thereon, which form a part of this specification.

Our invention relates to instruments that are placed in electriccircuits for the purpose of indicating the amount of current flowingtherein; commonly called ammeters.

The object of the invention is to simplify the construction and improvethe efficiency of the instrument, and the invention consists in certainfeatures hereinafter described and particularly pointed out in theclaims.

In the drawings, Figure l is a front elevation of an am meter embodyingour invention. Fig. 2 is a plan view. Figs. 3, 4 and 5 are details ofdampening or retarding devices. Figs. 6, 7 and 8 are details of loops.Fig. 9 is a blank for another form of loop. Fig. 10 shows edge, end andplan views of the blank bent into a loop. Figs. 11 and 12 are detailViews of the needle. Figs. 13, 14, 15 and 16 are modifications of theneedle; and Fig. 17 shows a modification in which the needles areinclosed in a removable frame.

In all the modifications shown the principle is the same, to wit:passing the electric current through a metallic bar so formed as tocarry the current on each side of the magnetic needle, or each of them.Any number of needles may be mounted on the spindle, which is weightedor otherwise adjusted to cause the needles to stand normally in linewith the bar, or preferably at a slight angle thereto, so that upon thepassage of the current the needles are deflected toward or to a positionat right angles with the bar, the angle of deflection depending upon thestrength of the current.

The parts are mounted upon a base A, of insulating material, such asslate, provided on its upper edge with a spirit level A. The conductingbar B is preferably horizontal, and at each end is a binding post B forconnecting the line wires. The middle portion of the bar is folded uponitself two or more times, as clearly shown in the drawings, forming aloop composed of two or more parallel folds, 1, 2, 3, between which isroom for the needle or needles C, rigidly mounted on the spindle D,which is stepped in jewel bearings. The inner bearing is adjustable,being set in the end of a screw 61, tapped into a hole in the innerfold 1. The outer bearing may be similarly mounted, as in Fig. 4; or itmay be held in the end of a rod d, adjustable by means of a set screw 01in a socket E, secured to a cross-bar F fastened by screws f to studs Gprojecting from the outer fold 3 of the loop. Suitable registeringholes'are formed in the middle and outer folds 2, 3, to receive thespindle, these holes being preferably lengthened into slots, asindicated in dotted lines,

to allow the needles to pass through them when the spindle is put intoplace or removed. By unscrewing the screws f and taking off thecross-bar F, the spindle with the needles, index H and counterweight H,can be removed from the bar. The index is light, so that its inertiaoffers practically no resistance to the movement of the needles. Itswings over a scale I, properly graduated in accordance with theascertained angles of defiection under known variations of current. Inpractice it is found that sixty degrees is the best range for the index;though we do not limit ourselves to any particular range. Thecounterweight is made to just balance the index. In order to bring theindex back to zero when the circuit is broken, a separate weight K isattached to the spindle, being adj ustable toward and away from thespindle, preferably by making it in the form of a nut traversing aradial screw 70. The end of the screw has a collar fitting the spindleand provided with a set screw whereby the screw can be angularlyadjusted on the spindle so as to bring the index exactly to zero when nocurrent is passing. The weight K is so adjusted on the screw that it isbarely enough to return the index without shock. The meter can be setperfectly horizontal by means of the spirit level A.

In order to lessen or eliminate the oscillation of the index, a brake ordamper is provided, consisting preferably of a copper disk L, mounted onthe spindle and rotating therewith. A magnet is arranged with its poles.

adjacent to opposite sides of the disk, so that the induced currentstend to retard the movement of the disk. Permanent horseshoe magnets Z Zmay be used, as shown in Figs. 3 and 4, the disk passing between theirpoles. Or, a strip of soft iron Z may be placed around the bar B,withits ends overlapping and far enough apart to permit the disk torotate between them. The current passing through the barB inducesmagnetism in the soft iron, and the lines of force passing acrossbetween its overlapping ends act to retard the disk.

The needles best suited forinstruments of this kind are made rather deepin the direc tion of the axis of the spindle and rather thintransversely thereto. long. i The reason for making the needle deep inthe direction of'the axis of the spindle, and thinin a directiontransverse thereto, is'to get sufficient mass for the lines of force toact on, and toiconfine them in such a narrow path thatthe needle iscompelled to place itself exactly in line with them. If the needle wasthicker, there would be a tendency to Whatis called cross-magnetization,and the needle would not place itself exactly in line.

Fig. 11 shows a simple needle, rectangular in cross section. Fig. 13shows two such nee dles, one being given a slight lead over the other toinsure their starting promptly, and in the right direction. Ithas beenfound that it is essential to give one or both of the-needles a lead of(say) fifteen degrees, since otherwise if they stood parallel with thebar they would be on a dead center, and might start in the wrongdirection. leadis, however, immaterial, and we do not limit ourselves toany specific number of degrees.

Fig. 14 shows a needle diamond-shaped in plan. Fig. 15 shows ahollowdiamond. Fig.

They need not be very of the loop.

- folds of the loop.

The particular amount of r in plan view a battery of six loops arrangedin two groups of three each, placed side by side and insulated from eachother. Insulating washers n are placed between thegroups, and insulatedbolts 0 hold all the loops together. The spindle D passes through theopening between the two groups. The loops are connected in series bymeans of metal strips, placed preferably on the back of the base A, andinsulated from each other. These strips are indicated by the dottedlines in Fig. 7. In the loops shown in Fig. 8, the current flows twiceby each needle, but in opposite directions to Fig. 6; that is to say, inFig. 6 the current flows to the right under each needle and to the leftabove them; while in Fig. 8 it flows to the right under oneand to theleft under the other, and vice versa over them. These loops in Fig. 8can be readily cut out with dies, or maybe cast. The inside end of oneloop is connected withthe outside end of the next, by the bentstrip ofmetal I).

Fig. 9 shows a blank of sheet metal, which when properly folded on thedotted" lines makes the loop shown in Fig. "10.

In case -it is desired to have one size of needles serve for a number ofinstruments of largely varying capacity, the spindle carrya ing theneedles andindex is mounted in jewel bearings in aframe or tube P, whichis insorted into registering holes cut in the folds To keep thetubeinproper alignment, it is provided with an external rib or key 19, whichengages'a slot in one or more By making all the instruments with holesof a standard size, one size of needles can be used for all, and readilyin-. serted or removed.

Having thus described our invention,'what. we claim as new is- 1. Anammeter oonsistingof the combina-f tion with a conducting bar foldedinto three or more folds with spaces between them, the outer foldscontaining registering holes, of a spindle, two or more magnetic needlesmounted thereon and adapted to pass through said holes with the spindle,and turn freely inthe spaces aforesaid, and suitable bearings for.

dle made deep in the direction of the axis of the spindle and thin in adirection transverse thereto, substantially as described.

5. An ammeter having its spindle mounted In testimony whereof we affixour signatures in a frame removable bodily from the conin presence oftwo witnesses. ducting bar without disturbing the mounting of thespindle, substantially as described.

6. An ammeter comprisinga spindle mounted in a tube fitting intoregistering holes in Witnesses: the folds of a folded conducting bar,substan- J 0s. A. LYNCH, tially as described. WM. E. BANTA.

EDWARD R. KNOWLES. LEWIS T. ROBINSON

